Rainfall intensity affects runoff responses in a semi-arid catchment     

Ze Tao  Min Li  Bingcheng Si  Dyan Pratt 《水文研究》2021,35(4):e14100

The source and hydrochemical makeup of a stream reflects the connectivity between rainfall, groundwater, the stream, and is reflected to water quantity and quality of the catchment. However, in a semi-arid, thick, loess covered catchment, temporal variation of stream source and event associated behaviours are lesser known. Thus, the isotopic and chemical hydrographs in a widely distributed, deep loess, semi-arid catchment of the northern Chinese Loess Plateau were characterized to determine the source and hydrochemical behaviours of the stream during intra-rainfall events. Rainfall and streamflow were sampled during six hydrologic events coupled with measurements of stream baseflow and groundwater. The deuterium isotope (²H), major ions (Cl⁻, SO₄²⁻, NO₃⁻, Ca²⁺, K⁺, Mg²⁺, and Na⁺) were evaluated in water samples obtained during rainfall events. Temporal variation of ²H and Cl⁻ measured in the groundwater and stream baseflow prior to rainfall was similar; however, the isotope compositions of the streamflow fluctuated significantly and responded quickly to rainfall events, likely due to an infiltration excess, overland dominated surface runoff during torrential rainfall events. Time source separation using ²H demonstrated greater than 72% on average, the stream composition was event water during torrential rainfall events, with the proportion increasing with rainfall intensity. Solutes concentrations in the stream had loglinear relationships with stream discharge, with an outling anomaly with an example of an intra-rainfall event on Oct. 24, 2015. Stream Cl⁻ behaved nonconservative during rainfall events, temporal variation of Cl⁻ indicated a flush and washout at the onset of small rainfall events, a dilution but still high concentration pattern in high discharge and old water dominated in regression flow period. This study indicates rainfall intensity affects runoff responses in a semi-arid catchment, and the stored water in the thick, loess covered areas was less connected with stream runoff. Solute transport may threaten water quality in the area, requiring further analysis of the performance of the eco-restoration project.  相似文献   

中国草畜平衡状态时空演变指示的草地生态保护格局   总被引：2，自引：0，他引：2  

黄麟  翟俊  祝萍  郑瑜晗 《地理学报》2020,75(11):2396-2407

中国草原牧区作为重要生态安全屏障和草地畜牧业生产基地,其草畜平衡状态直接影响草地退化与恢复,进而影响草地生态系统服务能力的强弱。本文分析了2000—2015年主要草原牧区草地植被覆盖、牧草供给、草畜平衡状态的时空变化特征,深入探讨草地退化与恢复及载畜压力下草地生态系统保护与恢复空间格局。结果表明：过去16年主要草原牧区草地面积净减少约163万hm²,6.7%的草地出现植被覆盖退化,而5.4%的草地呈现植被覆盖明显恢复。天然草地牧草供给量以增加为主,年增率约0.3 kg/hm²,然而其载畜压力亦持续增加,不考虑补饲的载畜压力指数高达3.8,除内蒙古东北部、青藏高原中部仍有载畜潜力,其余多处于超载状态;考虑实际冷季补饲的载畜压力指数约3.1,内蒙古中东部有所缓解;假设冷季全额补饲则载畜压力指数减至1.9,内蒙古、青藏高原等区域明显缓解。叠加上述数据,本文针对自然保护地、牧区、半农半牧区和农区等不同区域的草地生态保护格局,提出了平衡草地生态保护与畜牧生产利用的不同发展策略。  相似文献   

广盐性鱼类渗透压适应性与生理可塑性机制研究     

马爱军  崔文晓  刘志峰  张金生  黄智慧  杨双双  刘晓菲  杨凯  张薇 《海洋与湖沼》2018,49(6):1308-1317

拥有强大的渗透压调节能力对广盐性鱼类的生存至关重要。目前,关于鱼类渗透压调节机制已有不少研究,但均存在较大的局限性。本文从广盐性鱼类渗透压信号转导机制、渗透胁迫的细胞调控机制、渗透调控的内分泌调节机制和无机离子通道和转运蛋白介导的渗透调控等方面对广盐性鱼类的渗透压适应性和生理可塑性机制进行分析,以期从分子、细胞、通路和生理等层次初步探索广盐性鱼类盐度胁迫后的可塑性表型变化和不同盐度条件下的应答机制,为广盐性鱼类的渗透压调节机制的深入研究奠定基础。对广盐性鱼类渗透压适应性与生理可塑性机制研究,有助于研究其环境适应机理,促进野生鱼种的人工化养殖以及新品种的育种从而提高经济效益、社会效益和生态效益,对促进水产养殖学进步以及养殖业的发展具有重要意义,同时,为研究广盐性鱼类的渗透压调节机制开辟新的研究方向。  相似文献   

隧道工程地质评价的内容和方法   总被引：2，自引：0，他引：2  

陈新建  孙琳  李新星  孙巧银 《地球科学与环境学报》2004,26(1):41-45

结合工程隧道实际,首先阐述了隧道工程的基本地质环境和工程地质条件,然后针对隧道工程可能出现的不良地质现象和可采取的工程措施,从大气降水、围岩稳定、围岩压力、洞口稳定、隧道比选等角度探讨隧道工程地质评价的主要方法和一般内容,进行隧道工程地质评价,为隧道施工、支护提供了依据.  相似文献   

Modelling of deformation response and chemo‐mechanical coupling in chalk     

S. Pietruszczak  D. Lydzba  J. F. Shao 《国际地质力学数值与分析法杂志》2006,30(10):997-1018

A constitutive relation is derived for describing the mechanical response of chalk. The approach is based on a phenomenological framework which employs chemo‐plasticity. The properties of the material are assumed to be affected by the physico‐chemical processes that occur through the interaction between the skeleton and the pore fluid. The underlying mechanism is discussed by invoking a micromechanical analysis. The performance of the framework is illustrated by examining the evolution of mechanical characteristics in the presence of different pore fluids. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Size and shape evolution of pores in a viscoplastic matrix under compression     

M. Berli  M. L. Accorsi  D. Or 《国际地质力学数值与分析法杂志》2006,30(12):1259-1281

The frequent use of soils and earth materials for hydraulic capping and for geo‐environmental waste containment motivated our interest in detailed modelling of changes in size and shape of macro‐pores to establish links between soil mechanical behaviour and concurrent changes in hydraulic and transport properties. The objective of this study was to use finite element analysis (FEA) to test and extend previous analytical solutions proposed by the authors describing deformation of a single macro‐pore embedded in linear viscoplastic soil material subjected to anisotropic remote stress. The FEA enables to consider more complex pore geometries and provides a detailed picture of matrix yield behaviour to explain shortcomings of approximate analytical solutions. Finite element and analytical calculations agreed very well for linear viscous as well as for viscoplastic materials, only limited for the case of isotropic remote stress due to the simplifications of the analytical model related to patterns and onset of matrix‐yielding behaviour. FEA calculations were compared with experimental data obtained from a compaction experiment in which pore deformation within a uniform modelling clay sample was monitored using CAT scanning. FEA predictions based on independently measured material properties and initial pore geometry provided an excellent match with experimentally determined evolution of pore size and shape hence lending credence to the potential use of FEA for more complex pore geometries and eventually connect macro‐pore deformation with hydraulic properties. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

地下洞库勘察中的深斜孔钻探和压水试验技术          下载免费PDF全文

吉孟瑞  孙桂明  吴昌庆  原华山 《山东国土资源》2001,17(2):56-60

青岛市黄岛区拟建设海底地下油气储藏库,前期地质勘察工作要求施工倾角45°、深220m的取心钻孔4个,并在孔内分段进行压水试验.本文介绍了如何利用XY-4型金刚石小口径钻机施工基岩深斜孔及压水试验技术.  相似文献   

Formation Pressure Evaluation Method for Single Well     

WANG Yachun 《东北亚地学研究》2002,(1)

The paper deals with the methods of formation pressure evaluation for a single well by using the very common ac-cepted parameters, such as drilling exponent , and flowline temperature , etc. which is part of compiling the end well report.  相似文献   

Viscoelastodynamics of A Stratified, Compressible Planet: Incremental Field Equations and Short- and Long-Time Asymptotes     

Detlef Wolf 《Geophysical Journal International》1991,104(2):401-417

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Discriminating between pore‐filling load and bed‐structure load: a new porosity‐based method,exemplified for the river Rhine     

ROY M. FRINGS  MAARTEN G. KLEINHANS  STEFAN VOLLMER 《Sedimentology》2008,55(6):1571-1593

Sediments contained in the river bed do not necessarily contribute to morphological change. The finest part of the sediment mixture often fills the pores between the larger grains and can be removed without causing a drop in bed level. The discrimination between pore‐filling load and bed‐structure load, therefore, is of practical importance for morphological predictions. In this study, a new method is proposed to estimate the cut‐off grain size that forms the boundary between pore‐filling load and bed‐structure load. The method evaluates the pore structure of the river bed geometrically. Only detailed grain‐size distributions of the river bed are required as input to the method. A preliminary validation shows that the calculated porosity and cut‐off size values agree well with experimental data. Application of the new cut‐off size method to the river Rhine demonstrates that the estimated cut‐off size decreases in a downstream direction from about 2 to 0·05 mm, covariant with the downstream fining of bed sediments. Grain size fractions that are pore‐filling load in the upstream part of the river thus gradually become bed‐structure load in the downstream part. The estimated (mass) percentage of pore‐filling load in the river bed ranges from 0% in areas with a unimodal river bed, to about 22% in reaches with a bimodal sand‐gravel bed. The estimated bed porosity varies between 0·15 and 0·35, which is considerably less than the often‐used standard value of 0·40. The predicted cut‐off size between pore‐filling load and bed‐structure load (D_c,p) is fundamentally different from the cut‐off size between wash‐load and bed‐material load (D_c,w), irrespective of the method used to determine D_c,p or D_c,w. D_c,w values are in the order of 10^?1 mm and mainly dependent on the flow characteristics, whereas D_c,p values are generally much larger (about 10⁰ mm in gravel‐bed rivers) and dependent on the bed composition. Knowledge of D_c,w is important for the prediction of the total sediment transport in a river (including suspended fines that do not interact with the bed), whereas knowledge of D_c,p helps to improve morphological predictions, especially if spatial variations in D_c,p are taken into account. An alternative to using a spatially variable value of D_c,p in morphological models is to use a spatially variable bed porosity, which can also be predicted with the new method. In addition to the morphological benefits, the new method also has sedimentological applications. The possibility to determine quickly whether a sediment mixture is clast‐supported or matrix‐supported may help to better understand downstream fining trends, sediment entrainment thresholds and variations in hydraulic conductivity.  相似文献